Bifocal lenses are comprised of two or more areas, or zones, with different optical powers, including typically a far-power Optic Zone for distance vision, and a near-power Optic Zone for near or close up vision. The two zones may be subdivided into additional power zones in which case a lens may be called a multifocal lens.
Effective use of a bifocal contact lens requires translation of an ocular system between vision surfaces when an eye changes from gazing at an object at a distance to gazing at a nearby object. Alternatively, there may be a desire to have a translating multifocal contact lens that may have one or more intermediate-power zones in addition to far and near-power Optic Zones. Such a translating contact lens may have to have an ability to control and optimize the amount of movement of a lens when the pupil translates from distance vision, to intermediate vision, to near vision, or any combination thereof.
While there are many designs for soft translating contact lenses, soft contact lenses have difficulty translating across the surface of an eye when the visual direction of an eye changes from a straight-ahead gaze, to a downward gaze. In one prior art example, describes a soft bifocal contact lens that has an integrally formed bevel to aid translation of a lens. While other designs may have the capability to translate across the surface of an eye when the visual direction of an eye changes from a straight-ahead gaze, to a downward gaze, but are not very efficient at controlling movement of a lens during an eye's translation to a different visual direction. Another prior art example, describes a soft multifocal contact lens that has an integrally formed ramped ridge zone adjoining an outwardly extending latitudinal ridge that sits on an eyelid to aid in translation of a lens. The latitudinal ridge portion has a bump at each end, thereby increasing elevation height of the ends of the ridge compared to the elevation height in the middle. Another disadvantage of the prior art is discomfort when worn upon an eye.
Therefore, there is a need for a soft translating multifocal contact lens that provides various design options and is capable of limiting the amount of translation across the surface of an eye when an eye changes position from one Optic Zone to another while also providing wearers with improved comfort.